<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div class="a"></div>
    <div class="b" id="myBox"></div>
  </body>
  <style>
    .a {
      width: 250px;
      height: 250px;
      background-color: aqua;
    }

    .b {
      width: 400px;
      height: 100px;
      background-color: bisque;
    }
  </style>
  <script>
    const box = document.getElementById("myBox");
    box.style.marginTop = "15px";
    box.style.marginLeft = "15px";

    let wl = 10;

    // let num = 0;
    setInterval(() => {
      wl += 10;
      stringwl = wl + "px";
      box.style.marginLeft = stringwl;
      console.log(stringwl);
    }, 1000);
  </script>
</html>
